[REF] Extract transferParticipantRegistration function

[REF] Extract transferParticipantRegistration function

This is the extraction portion of https://github.com/civicrm/civicrm-core/pull/16956/

On testing that I hit  an error but getting the extraction merged first should make it easierr
to review future iterations as it  will reduce noise in the code.

Note I made the  function non-static since it is still on the form & passed in
event ID since we have it but it's otherwise pretty much the same as the
extraction part of that PR